protected override void OnClosing(CancelEventArgs e){  if(this.Visible)  {    e.Cancel=true;　　　//　　 // WHATE TODO 　　 //  }}

protected override void WndProc(ref Message m){const int WM_SYSCOMMAND = 0x0112;const int SC_CLOSE = 0xF060;if (m.Msg == WM_SYSCOMMAND && (int) m.WParam == SC_CLOSE){// User clicked close buttonthis.WindowState = FormWindowState.Minimized;return;}base.WndProc(ref m);}

private void richTextBox1_KeyDown(object sender, System.Windows.Forms.KeyEventArgs e){if(e.Control && e.KeyCode==Keys.V)e.Handled = true;}

#region 單實(shí)例運(yùn)行/// <summary>/// 單實(shí)例運(yùn)行/// </summary>/// <param name="frm">所要運(yùn)行的主窗體</param>public static void SingleRun(Form frm){  System.Threading.Mutex mutex = new System.Threading.Mutex(false,"SINGLE_INSTANCE_MUTEX");  if (!mutex.WaitOne(0, false))  { mutex.Close(); mutex = null;  }  if (mutex != null)  { Application.Run(frm);  }  else  { MessageBox.Show("應(yīng)用程序已啟動(dòng)","信息提示",MessageBoxButtons.OK,MessageBoxIcon.Information);  }}#endregion

 #region 將控件轉(zhuǎn)換為圓形 [System.Runtime.InteropServices.DllImport("gdi32")] private static extern IntPtr BeginPath(IntPtr hdc); [System.Runtime.InteropServices.DllImport("gdi32")] private static extern int SetBkMode(IntPtr hdc,int nBkMode);  const int TRANSPARENT=1; [System.Runtime.InteropServices.DllImport("gdi32")]    private static extern IntPtr EndPath(IntPtr hdc); [System.Runtime.InteropServices.DllImport("gdi32")] private static extern IntPtr PathToRegion(IntPtr hdc); [System.Runtime.InteropServices.DllImport("gdi32")] private static extern int Ellipse(IntPtr hdc,int x1,int y1,int x2,int y2); [System.Runtime.InteropServices.DllImport("user32")] private static extern IntPtr SetWindowRgn(IntPtr hwnd,IntPtr hRgn,bool bRedraw); [System.Runtime.InteropServices.DllImport("user32")] private static extern IntPtr GetDC(IntPtr hwnd); /// <summary> /// 將控件轉(zhuǎn)為圓形 /// </summary> /// <param name="control">控件名</param>  public static void MakeControlToCircle(Control[] control) {  IntPtr dc;  IntPtr region;  for(int i=0;i<control.Length;i++)  {  dc=GetDC(control[i].Handle);  BeginPath(dc);  SetBkMode(dc,TRANSPARENT);  Ellipse(dc,0,0,control[i].Width-3,control[i].Height-2);  EndPath(dc);  region=PathToRegion(dc);  SetWindowRgn(control[i].Handle,region,false);  }   }  #endregion

/// <summary>/// 在同一應(yīng)用程序中同一窗體只打開一個(gè)/// </summary>/// <param name="frmOpen">要打開的窗體實(shí)例</param>/// <returns></returns>public static void OpenSeamForm(Form frmOpen){  foreach (Form frm in Application.OpenForms)  { if (frm.Text == frmOpen.Text) {   frm.Visible = true;   frm.WindowState = FormWindowState.Normal;   frm.Activate();   return; }  }  frmOpen.Show();}